Worker now self-clocks; no heartbeats needed

GameRunner exposes pending work via a new hasPendingTurns() so the worker can check whether more ticks need to be processed.
Worker auto-runs ticks: as soon as it initializes or receives a new turn, it calls processPendingTurns() and loops executeNextTick() while hasPendingTurns() is true. No more "heartbeat" message type; the worker no longer depends on the main thread’s RAF loop to advance the simulation.
Client main thread simplified:
Removed CATCH_UP_HEARTBEATS_PER_FRAME, the heartbeat loop, and the lastBeatsPerFrame tracking.
keepWorkerAlive now just manages frame skipping + draining. When it decides to render (based on renderEveryN), it drains pendingUpdates, merges them, updates GameView, and runs renderer.tick().
Because rendering a batch always implies draining, we restored the invariant that every GameView.update is paired with a layer tick() (no more lost incremental updates).
MAX_RENDER_EVERY_N is now 5 to keep the queue from growing too large while the worker sprints.

src/client/ClientGameRunner.ts

@@ -216,7 +216,6 @@ export class ClientGameRunner {
   private catchUpMode: boolean = false;
   private readonly CATCH_UP_ENTER_BACKLOG = 120; // turns behind to enter catch-up
   private readonly CATCH_UP_EXIT_BACKLOG = 20; // turns behind to exit catch-up
-  private readonly CATCH_UP_HEARTBEATS_PER_FRAME = 5; //upper bound on heartbeats per frame when in catch-up mode
 
   private pendingUpdates: GameUpdateViewData[] = [];
   private isProcessingUpdates = false;
@@ -225,8 +224,7 @@ export class ClientGameRunner {
   private renderEveryN: number = 1;
   private renderSkipCounter: number = 0;
   private lastFrameTime: number = 0;
-  private readonly MAX_RENDER_EVERY_N = 60;
-  private lastBeatsPerFrame: number = 1;
+  private readonly MAX_RENDER_EVERY_N = 5;
 
   constructor(
     private lobby: LobbyConfig,
@@ -317,7 +315,6 @@ export class ClientGameRunner {
         this.processPendingUpdates();
       }
     });
-    const worker = this.worker;
     const keepWorkerAlive = () => {
       if (this.isActive) {
         const now = performance.now();
@@ -327,14 +324,6 @@ export class ClientGameRunner {
         }
         this.lastFrameTime = now;
 
-        const beatsPerFrame = this.catchUpMode
-          ? this.CATCH_UP_HEARTBEATS_PER_FRAME
-          : 1;
-        this.lastBeatsPerFrame = beatsPerFrame;
-        for (let i = 0; i < beatsPerFrame; i++) {
-          worker.sendHeartbeat();
-        }
-
         // Decide whether to render (and thus process pending updates) this frame.
         let shouldRender = true;
         if (this.catchUpMode && this.renderEveryN > 1) {
@@ -541,7 +530,6 @@ export class ClientGameRunner {
           this.backlogTurns,
           this.catchUpMode,
           this.renderEveryN,
-          this.lastBeatsPerFrame,
         ),
       );